I know a man who has a somewhat clear presentation on protons being imagined as: POSITRON::ELECTRON::POSITRON . First of all, did you realize that one charge can attract two (or more?) opposites? The mutual repulsion is less in the above scheme, than attraction. The humor is gigantic: WHERE DID ALL THE ANTIMATTER GO? LONG TIME PASSING... This I present of a paper from Charles Southwood, just for fun.

But wouldn't the electron and positron react with each other?

 

And wouldn't that make Up Quarks just positrons and the Down Quark an electron?

 

Which would make the Neutron two electrons and a positron, which would give it a negative charge...

Yes but attraction balanced by orbit, as always. Think positronium. I probably do not know enough to answer you but wish you would carry on! It's too outrageous of an idea not to. The interesting semi-classical argument he makes is that particles in high-velocity orbit will have foreshortened longitudinal fields and blown-out tranverse fields so there is a corresponding increase of radial magnitudes. He pictures neutrons as two plus two. Placed in a circle it looks not stable but it is true that they by themselves are not, and also that the 'in-line' fields between them are greatly reduced. (PS-I'll send you colored chalks for your Calabi-Yau.)

Positronium has a finite lifetime. So how do you account for the stability of the proton, the instability of the neutron and the masses of the systems? How can the spin of the neutron be 1/2 ?

I agree and am not defending this! It is such a huge guffaw to entertain the possiblity that somehow the antimattter didn't go away that I had to present Southwood's ideas. In my post on plasma recombination (Cosmology) I seek to learn about the baryon asymmetry in big bang cooling.